Ramaswamy Sakthivadivel

Limits to leapfrogging: issues in transposing successful river basin management institutions in the developing world

In Mollinga, P. P.; Dixit, A.; Athukorala, K. (Eds). Integrated water resources management: global theory, emerging practices and local needs. New Delhi, India: Sage

Land and water productivity of wheat in the Western Indo-Gangetic Plains of India and Pakistan: a comparative analysis

In Kijne, J. W.; Barker, R.; Molden. D. (Eds.). Water productivity in agriculture: limits and opportunities for improvement. Wallingford, UK: CABI; Colombo, Sri Lanka: International Water Management Institute (IWMI)Comprehensive Assessment of Water Management in Agriculture Series 1

A simple water balance modelling approach for determining water availability in an irrigation tank cascade system

Abstract This paper presents a water balance model Cascade formulated to account for the dynamic hydrologic components of an irrigation tank cascade system in Anuradhapura, Sri Lanka. The model is designed to estimate tank water availability on a daily basis, for the purpose of improving productive use of water resources in the tank cascade system. It represents the physical system using a node–link system configuration, and incorporates water balance components of different types of irrigation tanks including rainfall runoff, rainfall on tank, evaporation of tank water, tank seepage and percolation, irrigation water release, spillway discharge and return flow from upstream tanks. An important feature of Cascade is that it employs a modified runoff coefficient method for estimating runoff from rainfall, which incorporates a modified Antecedent Precipitation Index as an indicator of catchment wetness. This provided a simplified method for representing the non-linear runoff generation process. The model calculates tank seepage and percolation based on functions derived from an analysis of the observed tank water reduction during time periods without rainfall. The model was calibrated using field data collected at four tanks over a period of 21 months, which represented different agrometeorologic conditions encountered under both Maha and Yala growing seasons at the Thirappane tank cascade system in Anuradhapura, Sri Lanka. The model results agreed well with the measured data particularly in the two tail end tanks of the cascade, and clearly manifested the relative magnitudes of the tank water balance components and their temporal variations. An independent validation of the model could not be performed with the available data and thus the predictive capability of the model is not evaluated. The results of this study suggests that, with further improvements, the simple water balance modelling approach used in the model could potentially provide a basis for the development of a useful tool in the process of optimising usage of the limited water resources in similar tank cascade systems.

Cumulative relative water supply: A methodology for assessing irrigation system performance

This paper discusses the usefulness and limitations of using the concept of Relative Water Supply (RWS) for evaluating the performance of irrigation systems, with special reference to systems irrigating rice. It then describes and demonstrates the use of a modification of RWS called Cumulative Relative Water Supply (CRWS), which can be used in conjunction with RWS. The advantage of CRWS is that it provides a measure of the cumulated RWS throughout a season, both in absolute terms at any given time, and in terms of the overall seasonal trend. It allows comparison of performance of an irrigation system or subsystem both to the target, and to other systems or subsystems. It can therefore be used both as an analytical tool by researchers, and as an operational tool by managers. The use of CRWS in conjunction with RWS is illustrated with examples from Sri Lanka.

Maintenance Management Process

A case study from Maharashtra comparing maintenance performance between two transferred minor canals on the one hand and two non-transferred minor canals on the other is presented. It is shown that the clear differences in maintenance performance are due not to differences in resources expended, but to differences in maintenance management processes. This study demonstrates that small differences in management process can lead to major differences in maintenance performance under severe resource constraints.

Impact Assessment of Organizing Farmers in the Gal Oya Left Bank Irrigation Scheme, Sri Lanka

The nature and intensity of institutional interventions at the secondary unit level in the rehabilitation of the Gal Oya Left Bank irrigation system were different. The focus of this paper is to examine the impacts of these different interventions on the performance of secondary units using a time-series impact assessment model. The impact assessment model appears to be able to describe with some precision the trends in the system as a whole, as well as distinguish between different impacts in different units. The results of the analysis demonstrate that areas that were intensively organized showed the greatest capacity to adopt improved management techniques quickly. However, these well-organized areas also happened to be more favoured before rehabilitation and have realized least satisfactory overall benefits. Tail-end areas, even though they were less intensively organized, showed the best overall performance in terms of water use, production and water productivity. But they took longer to respond full...

Managing Groundwater in Hard-rock Areas through Agro-well Design and Development

Water shortage in the dry season is a major problem facing agriculture in the dry and intermediate zones of Sri Lanka. Large diameter wells (agro-wells) have been introduced to use the groundwater as a supplement to rainfall. The underlying crystalline hard-rock formations have very low storage and transmissivity, which limit the groundwater resource. The haphazard development of agro-wells may seriously threaten sustainable groundwater use in the future. Based on field studies and a groundwater hydrological model, this paper explains a methodology for determining the dimensions of agro-wells that limit a farmer to abstracting no more than the volume of water recharged under his/her land. This methodology can be used to regulate groundwater in hard-rock aquifers by identifying the safe volume of water that can be abstracted, establishing the optimum well dimensions for constructing a new well, and matching crop-water requirements to the abstractable volume of water. Farmers themselves can regulate groundw...

Water Resources Development Planning in a Basin Context in the Absence of Good Hydrologic Data: An Example from Sri Lanka

This paper describes a methodology for planning rehabilitation of small-scale irrigation systems in dry zones where the hydrologic database is poor. The methodology includes a two-stage decision-making process. The first stage relates to selection of cascades (meso-watersheds) within the basin for rehabilitation planning. The second stage is concerned with selection of tanks within a cascade and the type of rehabilitation components to be planned, taking into consideration the resource potential of the cascade and the socioeconomic factors of farmers. The methodology has been field-tested in Sri Lanka and shown to be efficient. A key principle underlying this approach is that development of any use of water within a basin must be viewed in the context of the whole basin to avoid conflicts over water use. Another principle is that hydrological and non-hydrological criteria must be used together to evaluate water resources development proposals.